Ink jet recording apparatus

ABSTRACT

An ink jet recording apparatus supplying a nozzle with ink through an ink passage from an ink tank and ejecting the ink from the nozzle for printing wherein there is provided in the ink passage a means for removing air carried into the ink. The air removal means includes a supplementary ink holder and a valve which couples the receptacle during a non-printing period for removal of the air.

United States Patent 1191 Ishii 1 Apr. 16, 1974 INK JET RECORDING APPARATUS [56] References Cited [75] Inventor: Hiroshi Ishii, Sagamiko-machi, UNITED STATES PATENTS Japan 3,083,689 4/1963 Hegener 346/140 Assigneez Casio Computer Ltd. y 3,708,798 1/1973 H1ldenbrand et a1. 346/140 Japan Primary Examiner.loseph W. Hartary Filed! 1972 Attorney, Agent, or Firm-Flynn & Frishauf [21] App]. No.: 315,905

[57] ABSTRACT An ink 'et recordin a aratus su 1 in anozzle with 30 FlAltPtDt J gPP PPYg l D Z i Ion y a a ink through an ink passage from an ink tank and eject- 1 46'335 ing the ink from the nozzle for printing wherein there DEC. Japan 1 1 is p d i e p ss ge a means f removing air carried into the ink. The air removal means in- 33ji2fl2 cludes a supplementary ink ho1der and a valve which I I a v v u u I l l u 1 1 s l v l I l l u 1 u I v v 1 I v I u u 1. l l [58] Field of Search 346/75, 140; 137/216, 217; g f fi gfi durmg a p'mtmg per'od 4 Claims, 3 Drawing Figures 20 AlR SUPPLEMENTARY INK HOLDER INK VALVE INK PASSAGE X7 7 INK H JEMPORARY INK RECEPTACLE TANK N OZ ZL E INK PAS SAGE APR SL974 PATENTED I 3,805,276

' SUPPLEMENTARY INK HOLDER VALVE INK 9 PASSAGE 7 WK H TQTEMPORARY INK RECEPTACLE TANK I5 46 NOZZLE PUMP INK PASSAGE INK CARTRIDGE F I 2 *25 SUPPLEMENTARY 49 INK HOLDER VALVE H EMPORARY INK RECEPTACLE J2 22 S T TANK g 16 NOZZLE 23 INK/ I DUCT INK PUMP INK F I G 3 PASSAGE RINT N P RIOD NOT B P I E PRINTING PERIOD 1ST VALVE 3RD VALVE V A V 2ND VALVE A I/ A INK JET RECORDING APPARATUS BACKGROUND OF THE INVENTION This invention relates to an ink jet recording apparatus for ejecting ink from a nozzle for printing and more particularly to an ink jet recording apparatus provided with a means for effecting distinct and stable printing.

An ink jet recording apparatus operates in intermittently ejecting ink supplied under pressure from an ink tank in fine particles through a nozzle having an inner diameter of about 1/10 mm by applying a high voltage electric field to the ink, and controlling the scattering direction of ink particles by a deflecting system so as to direct them to a sheet of recording paper for the printing of characters or the like. Distinct and stable printing by the above-mentioned apparatus requires ink particles to be ejected vfrom the nozzle in particles of proper size at an accurate interval.

However, it very frequently happens that air is carried into the ink held in an ink pump for supplying the ink under pressure to the nozzle as well as in an ink tank stored with ink' being conducted to the ink pump. Further, where the ink tank consists of a cartridge prepared from thin rubber film, the suction force of the pump is carried even to the interior of the cartridge, causing air to be carried into the ink stored in the car tridge through the thin rubber film. Moreover, there is the possibility of air being drawn into the ink while the ink pump is in operation. The amount of air introduced into the ink is indeed extremely small. Since, however, the nozzle has a very minute inner diameter, the ink being ejected from the nozzle tends to have its flow interrupted by the air contained therein. Further, a layer of air which might be present in the ink passage would make ink ejecting pressure irregular. Thus there result the drawbacks that ink particles can not be delivered from the nozzle under stable conditions at a regular interval, giving rise to the failure to attain clear and truthful printing of characters or the like on recording paper.

It is accordingly the object of this invention to provide an ink jet recording apparatus which unfailingly prevents air from being carried into the ink being supplied to the nozzle, thereby always permitting a stable printing operation.

SUMMARY OF THE INVENTION The ink jet recording apparatus of this invention is characterized in that the ink passage is provided with a means for eliminating air carried into the ink being supplied for printing from the ink tank to the nozzle through the ink passage.

An air removing device according to this invention may be operated in various modifications. One of these modifications may comprise, for example, providing a temporary ink receptacle, at least one part of which is made to extend upward, at the forward end of a first ink passage through which ink is carried under pressure from an ink pump and further providing a second ink passage communicating with the bottom opening of the ink receptacle so as to conduct ink to a nozzle. The air removing device of this invention further comprises a valve disposed at the upper end of the ink receptacle and designed to open during a nonprinting period and a supplementary ink holder. During opening of the valve, air is removed from the ink supply and is vented into the supplementary ink holder. Whereby the volume of air removed is replaced by an equal volume of ink from the supplementary ink holder. This embodiment of the invention can attain stable printing over a very long period.

A modification of said air removing device has a first BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows an air removing device according to one embodiment of this invention, wherein there are provided a temporary ink receptacle and supplementary ink holder between the ink pump and nozzle;

FIG. 2 illustrates an air removing device according to another embodiment of the invention, wherein there are provided a first valve between the ink tank and ink pump, a second valve between the temporary ink receptacle and supplementary ink holder and a third valve between the ink pump and nozzle; and

FIG. 3 indicates the operational relationship of the respective valves of FIG. 2.

Description of the Preferred Embodiments Referring to FIG. 1, an ink pump 11 draws off ink from an ink tank 12 and makes it flow under pressure through a first ink passage 13. A pipe comprising the first ink passage has an inner diameter of, for example, 1 to 2 mm. At the forward end of the first ink passage is disposed a temporary ink receptacle 14, at least one part of which is made to extend upward. This temporary ink receptacle comprises a pipe having an inner diameter of, for example, 2 to 3 mm. Under the ink receptacle 14 is laid a second ink passage 15 having an inner diameter of, for example, 1 to 2 mm so as tocommunicate with the bottom opening of the ink receptacle 14. To the outer end of the second ink passage 15 is fitted a nozzle 16. Where there is not used the later described supplementary ink holder, the upper portion of the temporary ink receptacle 14 is kept closed. According to this arrangement, ink is carried under pressure from the ink pump 11 through the first ink passage 13 to the ink receptacle 14, from which ink is conducted through the second ink passage 15 to the nozzle 16 to be ejected therefrom. As previously described, ink is delivered in fine particles by the action of a high voltage field, and later deflected by a deflecting system for the printing of characters or the like. However, the parts of the ink jet recording apparatus related to these operations are not indicated. The air which happens to be carried into the ink delivered under pressure from the ink pump 11 is separated from the ink when it is brought to the ink receptacle and collected in the upper part of said receptacle 14. Accordingly, only airfree ink is supplied to the nozzle 16, where the ink is saved from having its flow interrupted by the possible presence of air or the pressure with which the ink is ejected is prevented from being disturbed by said presence of air. Therefore, characters or the like can be printed distinctly under a stable condition.

Though it may be possible to trap more air by enlarging the capacity of the ink receptacle 14, yet there will arise the drawback that where increased volumes of air are collected in the upper part of said receptacle 14, then the pressure applied by the ink pump 11 will be partly absorbed in a layer of air thus collected to obstruct the smooth ejection of ink from the nozzle. Namely, mere provision of such ink receptacle would present difficulties in attaining good printing over a long period. To effect clear printing over a long period, it is advised to use the process which comprises further providing, as shown in FIG. 1, a supplementary ink holder 19 stored with ink 18 above the ink receptacle 14 with the valve 17 interposed between the holder 19 and receptacle 14; keeping the valve 17 closed while ink is ejected from the nozzle for printing and opened during a nonprinting period so as to allow the air already collected in the upper part of the receptacle 14 to escape into the holder 19. This valve 17 may comprise, for example, an electromagnetic valve actuated in response to the operation of the power source of a recording apparatus. According to the abovementioned process, the valve 17 remains closed during the printing period, enabling air-free ink to be supplied to the nozzle 16 with constant pressure as in the case where there is only provided the ink receptacle 14. Further, where printing is discontinued or the power source is shut off, the valve 17 is opened to allow the air previously collected in the upper part of the receptacle 14 to escape into the supplementary ink holder 19 and be held in the upper part 20 of said holder 19. Under such arrangement, there is gathered in the upper part of the ink receptacle 14 only the air trapped during a continuous printing period and the air thus trapped in the receptacle 14 is immediately carried into the supplementary holder 19 the moment printing is brought to an end. Therefore, even where a great deal of air iscollected in the receptacle 14, the air is immediately expelled into the supplementary holder 19 and the valve 17 closed thereafter prevents the back flow of air from said holder 19. Accordingly, the pressure applied by the ink pump 11 when operated next time will not be absorbed in the air which might otherwise remain in the receptacle 14, thereby enabling only air-free ink to be supplied to the nozzle 16 with constant pressure. The supplementary ink holder 19 is only required to have a capacity of about cc. Provision of a supplementary holder 19 having such a capacity permits clear and stable printing without the necessity of drawing off air therefrom for a period of even 5 to 7 years.

The arrangement of FIG. 2 is an improvement on the embodiment of FIG. 1. The parts of FIG. 2 the same as those of FIG. 1 are denoted by the name numerals. The embodiment of FIG. 2 has a first valve 23 provided in an ink duct 22 disposed between the ink tank 12 and ink pump 11, a second or aforesaid valve 17 between the ink receptacle 14 and supplementary ink holder 19 first and third valves are opened and closed, the moment they are closed. These valves may consist of, for example, electromagnetic valves actuated by electric signals from a recording apparatus.

Where printing is carried out by a recording apparatus of the above-mentioned arrangement, the first and third valves 23 and Marc opened by an electric signal representing a printing command supplied from said apparatus (the period A of FIG. 3 during which the second valve 17 remains closed). Ink flows into the ink tank 12 from the ink cartridge 25, and then to the pump 11 through the first valve 23 and ink duct 22.

and a third valve 24 in the ink passage laid between the When the pump 11 exerts pressure by the drive of a motor (not shown), ink is conducted through the first ink passage into the ink receptacle 14. The air which happens to be contained in the ink is removed in the receptacle 14 to be collected in the upper part. Thus only air-free ink is supplied under pressure through the third valve 24 to the nozzle 16 to be ejected therefrom. The ejected ink is deflected by an electric field created by a printing signal from a signal generator (not shown) for the printing of characters or the like.

Where printing is brought to an end or a used ink cartridge 25 is replaced by a fresh one, the first and third valves 23 and 24 are closed and the second valve 17 is opened (the period B of FIG. 3). The pump 11 and the cartridge 25 which is made of, for example, rubber are evacuated when the ink contained therein is drawn off beyond a prescribed limit and the cartridge contracts itself. This evacuated state of the pump is maintained by the closure of the first valve 23, thereby preventing air from being carried into the pump 11 when the used cartridge 25 is replaced by a fresh one. When the first valve 23 is opened for next printing, ink flows into the pump 11 to restore it to a normal operating state from the evacuated state. Even if the ink brought to the passage disposed between the pump 11 and nozzle 16 is subjected to an external shock or expanded due to change in temperature or atmospheric pressure, the ink is prevented from being retained at the nozzle tip or the ink retained at said nozzle tip is prevented from dripping therefrom to soil the interior of the recording apparatus as said third valve 24 is closed immediately after printing and the ink amount. The operational effect of the second valve 17 which is closed during a printing period and opened during a nonprinting period has already been explained, further description thereof being omitted.

The prior'art ink jet recording apparatus has often been accompanied with the drawbacks that where it is desired to use the apparatus a second time, air is carried into the ink passage, or the ink retreats from the nozzle to prevent a sufficient amount of ink for printing from being delivered from the nozzle, resulting in the indistinct printing or a complete failure of printing the first character or the like, and further the ink which happens to be retained at the nozzle tip drips therefrom to soil the interior of the recording apparatus. However, the ink jet recording apparatus of this invention has obviouly eliminated the above-mentioned difficulties by providing three valves and a device for removing the air entrained with the ink.

The ink ejected from the nozzle is later deflected by an electric field created by an electric signal supplied by the signal generator of a recording apparatus for the printing of characters or the like. In this case, it is possible to provide a plurality of recording apparatuses, si-

multaneously operate them, to print portions of an aggregation of characters or the like by each apparatus by shifting said plural recording apparatuses relative to a recording paper, thereby effecting efficient printing.

What is claimed is:

1. An ink jet recording apparatus comprising:

an ink pump for drawing ink from an ink tank for further delivery under pressure;

a temporary ink receptacle having a bottom opening and disposed at the forward end of a first ink passage through which the ink delivered from the pump flows under pressure, at least one part of the temporary receptacle extendingupward;

a nozzle for ejecting ink to effect printing;

a second ink passage communicating with the bottom opening of the temporary ink receptacle so as to supply ink to the nozzle;

a supplementary ink holder containing ink therein and disposed at the upper end of the temporary ink receptacle; and

a valve which is opened during a nonprinting period interposed between the supplementary ink holder and the upper end of the temporary ink receptacle so as to remove air from the temporary ink receptacle when the valve is opened.

2. Apparatus according to claim 1 wherein at least part of the supplementary ink holder is located above the level of the temporary ink receptacle.

3. An ink jet recording apparatus comprising:

a first valve provided in an ink passage between an ink tank and a pump drawing ink from the ink tank for further delivery under pressure;

a second valve provided between the top of a temporary ink receptacle and a supplementary ink holder containing ink to communicate the temporary ink receptacle with the supplementary ink holder, the temporary ink receptacle having a bottom opening and being disposed at the forward end of a first ink passage through which the ink delivered from the ink pump flows under pressure, at least one part of the temporary ink receptacle extending upward;

a nozzle for printing;

a second ink passage communicating with the bottom opening of the temporary ink receptacle so as to supply ink to the nozzle; and

a third valve disposed in said second ink passage between the ink pump and the nozzle, wherein the first and third valves are kept open while ink is ejected from the nozzle and are closed when ink ejection is brought to an end, and the second valve is closed when the first and third valves are opened, and is opened when first and third valves are closed so as to remove air from the temporary ink receptacle when the second valve is opened.

4. Apparatus according to claim 3 wherein at least part of the supplementary ink holder is located above the level of the temporary ink receptacle. 

1. An ink jet recording apparatus comprising: an ink pump for drawing ink from an ink tank for further delivery under pressure; a temporary ink receptacle having a bottom opening and disposed at the forward end of a first ink passage through which the ink delivered from the pump flows under pressure, at least one part of the temporary receptacle extending upward; a nozzle for ejecting ink to effect printing; a second ink passage communicating with the bottom opening of the temporary ink receptacle so as to supply ink to the nozzle; a supplementary ink holder containing ink therein and disposed at the upper end of the temporary ink receptacle; and a valve which is opened during a nonprinting period interposed between the supplementary ink holder and the upper end of the temporary ink receptacle so as to remove air from the temporary ink receptacle when the valve is opened.
 2. Apparatus according to claim 1 wherein at least part of the supplementary ink holder is located above the level of the temporary ink receptacle.
 3. An ink jet recording apparatus comprising: a first valve provided in an ink passage between an ink tank and a pump drawing ink from the ink tank for further delivery under pressure; a second valve provided between the top of a temporary ink receptacle and a supplementary ink holder containing ink to communicate the temporary ink receptacle with the supplementary ink holder, the temporary ink receptacle having a bottom opening and being disposed at the forward end of a first ink passage through which the ink delivered from the ink pump flows under pressure, at least one part of the temporary ink receptacle extending upward; a nozzle for printing; a second ink passage communicating with the bottom opening of the temporary ink receptacle so as to supply ink to the nozzle; and a third valve disposed in said second ink passage between the ink pump and the nozzle, wherein the first and third valves are kept open while ink is ejected from the nozzle and are closed when ink ejection is brought to an end, and the second valve is closed when the first and third valves are opened, and is opened when first and third valves are closed so as to remove air from the temporary ink receptacle when the second valve is opened.
 4. Apparatus according to claim 3 wherein at least part of the supplementary ink holder is located above the level of the temporary ink receptacle. 